I have a Colt MT HBAR, I know thw "C" means the barrel is chrome lined, but what does the "MP" stand for?

Manganese Phosphate finish?

Quoted: c mp = Colt  Magnetic Particle (Tested)

OK, that was my second guess.

Quoted: c mp = Colt  Magnetic Particle (Tested)

You mean magna fluxed...like a crankshaft?  Maybe, I've never heard that one.  A lot of people have told me the "C" stands for chrome, but who knows...that's why I'm asking.

Edited to say thanks, not second guessing you.  Your reply is the most logical thing I've heard so far.  Do you think Colt could give me an answer if I called?

Your Colt MT HBAR is NOT chrome lined. They stopped chrome lining their civie barrels a while back.

The C stands for Colt
The MP stands for Magnetic Particle inspected.

Jeepers you guys are good.  Since this has been bothering me for a whaile now, what is my upper that's marked E MP?

www.biggerhammer.net/ar15/barrelsbolts/

There is a difference between "magnaflux" (liquid penetration inspection)
and a magnetic particle inspection.

Magnaflux is the name of the company that developed the modern processes of "liquid penetration inspection"
www.cnde.iastate.edu/ncce/PT_CC/Sec.1.1/Sec.1.1.html
"Liquid Penetrant Testing (PT) - Test objects are coated with visible or fluorescent dye solution. Excess dye is then removed from the surface, and a developer is applied. The developer acts as blotter, drawing trapped penetrant out of imperfections open to the surface. With visible dyes, vivid color contrasts between the penetrant and developer make "bleedout" easy to see. With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen."

A magnetic particle inspection involves running a current of electricy through the part to magnatize it.

"The magnetic particle inspection method is one of the oldest and most widely utilized forms of nondestructive testing currently in use today. Magnetic particle testing uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components.  In theory, it is a relatively simple concept.   When a bar magnetis broken in the center of its length, two complete bar magnets with magnetic poles on each end of each magnet will result.   If the magnet were cracked but not broken completely in two, a north and south pole will form at each edge of the crack, just as though the break had been completed. If iron particles were then sprinkled on this cracked magnet, these particles will be attracted not only to the ends of the magnets poles but also to the edges of the crack."
www.cnde.iastate.edu/ncce/MT_CC/Principles.html

Quoted: Your Colt MT HBAR is NOT chrome lined. They stopped chrome lining their civie barrels a while back. The C stands for Colt The MP stands for Magnetic Particle inspected.

hmmmmmmm, don't be so sure about that, i read that ALL MILITARY contract barrels were chrome lined whether marked or not, i have a civie barrel and IT IS. And i'm talking about a new model, not an old one, hell i can even see the chrome linning in the chamber and bore, yeah chrome linning, not just a good polishing.
HUNTER FROM ARGENTINA
OUT.

Not sure about the MP but "C" is for chrome according to all articles I've read.  Where's Troy...he will know.

sgtar15

I still see no mention of the "E" MP.

My upper is marked: E MP 5.56 NATO 1/7

Any one know what the  E stands for?


.

Thanks Troy, that's what I thought.  Damn, and I just gave it to my wife for Christmas!